Solvent-free process for the preparation of diketopyrrolopyrrole derivatives

ABSTRACT

The present application relates to compounds of formula A(D) x (E) y , (I), compounds of formula (III), compounds of formula (X), as well as processes for the preparation thereof, processes where the compounds (I) are converted to pigments of formula (II) and the use of the compounds (I).

This is an application filed under 35 U.S.C. 371 of PCT/IB2003/002710.

The present invention relates to certain organic compounds, processesfor their manufacture, and their use. The invention particularly relatesto an essentially solvent-free process for the preparation of thealkali-metal salts of diketopyrrolopyrrole compounds, their use aslatent pigments and their use for the preparation of the correspondingdiketopyrrolopyrrole pigments in their suitable pigmentary form.

Latent pigments are described in EP-A 654 711, as are chemical, thermalor photolytic methods by means of which it is possible to generatefinely divided pigment particles in situ in substrates (see also U.S.Pat. Nos. 6,071,989, 6,211,347 and 6,365,720). It is also known thatlatent pigments can be used advantageously for the preparation ofpigment dispersions, and their use in colouring high molecular massmaterials (U.S. Pat. No. 6,211,347).

The process of making pigment derivatives as latent pigments is knownfrom EP 648 817 and WO 98/32802. In those processes, pigments arereacted inter alia with dicarbonates in a solvent, optionally in thepresence of a catalyst. A number of solvents are disclosed, includingalso aromatic solvents such as benzene, toluene, xylene, anisole,chlorobenzene and pyridine. Preference is given to the highly polarsolvents N,N-dimethylformamide, N-methyl-pyrrolidone or tetrahydrofuran.In the Examples, only N,N-dimethylformamide, N,N-dimethyl-acetamide ortetrahydrofuran are used.

It has been found, however, that that method does not always yieldsatisfactory results to the desired extent (see U.S. Pat. No. 6,365,720)some pigments produce inexplicably low yields or can be reacted onlypartially, with hydroxyl or amide groups. Other pigments react better,but the crude pigment derivatives obtained there from exhibitunsatisfactory purity or inadequate storage stability, so that complexpurification steps are necessary. Still further pigments give rise tounexpected problems on a pilot scale or production scale.

In U.S. Pat. No. 6,365,720 it has been claimed that certain pigments canbe used with surprisingly better results if the reaction is carried outwith a pyrocarbonic acid diester in an aromatic solvent. Both the yieldand the purity are markedly higher, and more groups can be incorporatedinto the pigment. The method according to this invention is also claimedto be excellently suitable especially for the production of latentpigments in relatively large amounts (.gtoreq.1 mol). Furthermore, it isalso claimed that surprising a more complete reaction is obtained in, ofall things, relatively non-polar solvents in which the pigments andsoluble pigment derivatives obtained there from are less soluble than insolvents used hitherto.

Both of these processes suffer from the serious disadvantages of economyand ecology. For example on one hand the processes for the preparationrequire use of solvents and very difficult to handle reactants, and onthe other hand are tedious and too elaborate to be of any commercialimportance. More serious disadvantage, however, is the fact thatpotentially explosive and toxic gases are generated when the pigmentsare derived from the corresponding latent pigments while beingincorporated into the substrate. Thus even the incorporation of latentpigments into the substrates can be extravagant, requiring specialequipment and handling measures.

It has now been found that alkali metal salts of certain pigments whichare easy to produce and readily hydrolyse or are induced to hydrolyse insitu to generate the corresponding pigment, are better suited as latentpigments particularly for liquid systems such as paints, printing inksand wood stains. They are particularly suitable for the preparation ofpigment dispersions, and their use for pigmenting high molecular massmaterial. The incorporation of such latent pigments does not require anyelaborate equipment. Moreover, no potentially hazardous organic volatilematerials are liberated thereby. The pigments thus generated in situ areauto-dispersed and do not need further dispersion equipment and/orprocess.

Accordingly, the invention relates to compounds of formula IA(D)_(x)(E)_(y)  (I)whereinx and y are each independently of the other an integer from 0 to 6, butx and y are not simultaneously 0,A is the radical or a mixture of radicals of a chromophore of thediketopyrrolopyrrole quinacridone, anthraquinone, perylene, indigo,quinophthalone, indanthrone, isoindolinone, isoindoline, dioxazine, azo,phthalocyanine or perinone series, which radical is bonded via one ormore nitrogen atoms to x groups D and via one or more oxygen atoms to ygroups E, the nitrogen atoms and oxygen atoms forming part of theradical A,each group D or E independently of any other(s) is an alkali metal.

The invention also relates to a method for preparing a compound of theformula A(D)_(x)(E)_(y) (I) by reaction of a compound of the formula IIA(H)_(x)(H)_(y)  (II)with a strong alkali metal base in the presence or absence of an organicsolvent at ambient to elevated temperature.

Examples of suitable solvents are primary, secondary or tertiaryalcohols containing 1 to 10 carbon atoms, e.g. methanol, ethanol,n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol,n-pentanol, 2-methyl-2-butanol, 2-methyl-2-pentanol,3-methyl-3-pentanol, 2-methyl-2-hexanol, 3-ethyl-3-pentanol,2,4,4-trimethyl-2-pentanol, or glycols such as ethylene glycol ordiethylene glycol; and also ethers such as tetrahydrofuran or dioxan, orglycol ethers such as ethylene glycol methyl ether, ethylene glycolethyl ether, diethylene glycol monomethyl ether or diethylene glycolmonoethyl ether; as well as dipolar aprotic solvents such asacetonitrile, benzonitrile, dimethylformamide, N,N-dimethylacetamide,nitrobenzene, N-methylpyrrolidone; aliphatic or aromatic hydrocarbonssuch as benzene or benzene substituted by alkyl, alkoxy or halogen, e.g.toluene, xylene, anisole or chlorobenzene; or aromatic heterocycliccompounds such as pyridine, picoline or quinoline. A mixture of solventsmay also be used. It is convenient to use 5 to 20 parts by weight ofsolvent per 1 part by weight of reactants.

Suitable strong bases include alkali metal hydroxides, alkali metalssuch as lithium, sodium and potassium, an alkali metal amide, an alkalimetal hydride; and alkali metal or alkaline earth metal alkoxidesderived in particular from primary, secondary or tertiary aliphaticalcohols having 1 to 10 carbon atoms. It is also possible to use amixture of the above mentioned alkali metal alkoxides. Preference isgiven to using alkali metal alkoxides and hydroxides with alkali metalbeing especially sodium or potassium, and the alkoxide is preferablyderived from a primary, secondary or tertiary alcohol. Particularlypreferred strong bases are for example potassium hydroxide, sodiummethylate, sodium isopropylate, sodium tert-butylate and sodiumtert-amylate. These alkali metal alkoxides can also be prepared in situby reacting the corresponding alcohol with alkali metal.

If an alcoholate is used as a base, it may also be used as a solution ora suspension in the same alcohol or in an inert solvent. The alcoholand/or the solvent thus used and formed during the reaction maycontinuously be distilled off during the reaction thereby providingsolvent-free reaction conditions.

A is preferably the radical of a chromophore of thediketopyrrolopyrrole, quinacridone, perylene, indigo, quinophthalone,isoindolinone, isoindoline, dioxazine, azo or the perinone series.

Further preference is given to derivatives having at least oneimmediately adjacent or conjugated carbonyl group at each nitrogen atombonded to x groups D. It is also possible, however, for a plurality, oreven all, of the groups D and/or E to be bonded to such nitrogen oroxygen atoms.

Particularly preferred compounds of formula I are thediketopyrrolopyrrole compounds of formula III

wherein both M represent an alkali metal and each of R₁ and R₂independently of the other is an isocyclic or heterocyclic aromaticradical. The radicals R₁ and R₂ may be different or identical, but arepreferably identical. R₁ and R₂ as isocyclic aromatic radicals arepreferably monocyclic to tetracyclic radicals, most preferablymonocyclic or bicyclic radicals, i.e. phenyl, biphenyl or naphthyl.Heterocyclic aromatic radicals R₁ and R₂ are preferably monocyclic totricyclic radicals. These radicals may be entirely heterocyclic or maycontain a heterocyclic ring and one or more fused benzene rings, and thecyano group can be linked both to the heterocyclic and to the isocyclicmoiety respectively. Examples of heterocyclic aromatic radicals are:pyridyl, pyrimidyl, pyrazinyl, triazinyl, furyl, pyrrolyl, thiophenyl,quinolyl, benzimidazolyl, quinazolyl, quinoxalyl, phthalazinyl,phthalazindionyl, phthalamidyl, isoquinolinyl, isothiazolyl, acridinyl,acridonyl, quinazolindionyl, quinoxadindionyl, benzoxazindionyl,benzoxazinonyl and naphthalimidyl.

Both the isocyclic and the heterocyclic aromatic radicals may containthe customary non-watersolubilising substituents such as:

(1) Halogen atoms, e.g. chlorine, bromine or fluorine atoms.

(2) Branched or unbranched alkyl groups containing preferably 1 to 18,especially 1 to 12, more particularly 1 to 8 and, most preferably, 1 to4 carbon atoms. These alkyl groups may contain non-watersolubilisingsubstituents, e.g. fluorine, —OCOR₅, —OR₆, —CONR₇ or —CONHR₈, wherein R₅and R₆ are alkyl, aryl such as napthyl, or benzyl or benzyl substitutedby halogen, alkyl or alkoxy, or a heterocyclic radical; R₇ and R₈ arehydrogen, alkyl or alkyl substituted by cyano or hydroxy, or C₇-C₈cycloalkyl, aryl or heteroaryl, especially phenyl or phenyl substitutedby halogen, alkyl or alkoxy, or R₇ and R₈ together with the nitrogenatom form a 5- or 6-membered heterocyclic ring, e.g. a morpholine,piperidine or phthalimide ring. Further possible substituents at thealkyl groups are mono- or dialkylated amino groups, aryl radicals suchas naphthyl or preferably phenyl or phenyl substituted by halogen, alkylor alkoxy, or also heterocyclic aromatic radicals such as 2-thienyl,2-benzoxazolyl, 2-benzthiazolyl, 2-benzimidazolyl, 6-benzimidazolonyl,2-, 3- or 4-pyridyl, or 2-, 4- or 6-quinolyl radicals.(3) Alkoxy groups containing preferably 1 to 18, especially 1 to 12,more particularly 1 to 8 and, most preferably, 1 to 4 carbon atoms.(4) A cyano group.

Examples of unsubstituted or substituted alkyl groups are: methyl,ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl,n-pentyl, n-hexyl, 1,1,3,3-tetramethylbutyl, n-heptyl, n-octyl, nonyl,decyl, undecyl, dodecyl, hydroxymethyl, trifluoromethyl, trifluoroethyl,cyanomethyl, methoxycarbonylmethyl, acetoxymethyl or benzyl.

Preferred meanings of R₁ and R₂ are phenyl or phenyl substituted by oneor two fluorine, chlorine or bromine atoms or mixtures thereof, by one,two or three methoxy or methyl groups or mixtures thereof with chlorineatoms, by cyano, by dimethylamino, by trifluoromethyl, by alkoxycarbonylof 2 to 3 carbon atoms, by tert-butyl, by cyanophenyl, by acetyl or byalkylbenzoyloxy of 11-14 carbon atoms; biphenyl; naphthyl or naphthylsubstituted by methoxy; anthryl; phenanthryl; pyridyl or pyridylsubstituted by methyl or by amyloxy; quinolyl; furyl or thienyl.

Besides the process of making compounds of Formula III from thecorresponding preferred compounds of formula IV

of the general formula II, the compounds of Formula III can also beprepared directly by essentially solvent free in situ synthesis, whichprocess comprises reacting 1 mole of a disuccinate of formula

wherein each R₃ and R₄ independently of the other is an alkyl or acycloalkyl or an aryl radical, with at the most 2 moles of a nitrile ofthe formulaR₁—CN  (VI)orR₂—CN  (VII)or with 0.1 to 1.9 mole of a nitrile of the formula VI and 1.9 to 0.1mole of the nitrile of the formula VII, essentially in the absence ofany organic solvent and in the presence of a strong base at elevatedtemperature. This process for the preparation of pigments of formula IVwithout use of a solvent is particularly preferred.

It is preferred in this connection to use nitrites of the formulae VIand/or VII, wherein R₁ and R₂ are unsubstituted phenyl or naphthyl orphenyl or naphthyl, which contain non-watersolubilising substituents.

In particular, the starting materials employed are nitrites of theformula VIII

wherein each of R₉, R₁₀ and R₁₁ independently of one another ishydrogen, fluorine, chlorine, bromine, cyano, trifluoromethyl, C₁-C₁₂alkyl, C₁-C₁₂ alkoxy, C₁-C₁₂ alkylmercapto, C₂-C₁₃ alkoxycarbonyl,C₂-C₁₃ alkanoylamino, C₁-C₁₂ monoalkylamino, C₂-C₂₄ dialkylamino orphenoxy, phenylmercapto, phenoxycarbonyl, phenylcarbamoyl orbenzoylamino, each unsubstituted or substituted by halogen, C₁-C₁₂ alkylor C₁-C₁₂ alkoxy, with the proviso that at least one of R₉, R₁₀ and R₁₁is hydrogen.

Most preferably, the starting materials employed are nitriles of theformula IX wherein one of R₁₂ and R₁₃ is chlorine, bromine, C₁-C₄ alkyl,cyano, C₁-C₄ alkoxy, or phenoxy, carbamoyl or C₂-C₅ alkylcarbamoyl, eachunsubstituted or substituted by chlorine or methyl, or phenylcarbamoylwhich is unsubstituted or substituted by chlorine, methyl or methoxy,and the other is hydrogen.

The disuccinates V to be used in the process of this invention may bedialkyl, dicycloalkyl or diaryl. The dialkyl, dicycloalkyl and diarylsuccinates may also be unsymmetrical. However, it is preferred to usesymmetrical disuccinates, most preferably symmetrical dialkylsuccinates.

Examples of disuccinates are dimethyl succinate, diethyl succinate,dipropyl succinate, dibutyl succinate, dipentyl succinate, dihexylsuccinate, diheptyl succinate, dioctyl succinate, diisopropyl succinate,di-sec-butyl succinate, di-tert-butyl succinate, di-tert-amyl succinate,di-[1,1-dimethylbutyl]succinate, di-[1,1,3,3-tetramethylbutyl]succinate,di-[1,1-dimethylpentyl]succinate, di-[1-methyl-1-ethylbutyl]succinate,di-[1,1-diethlylpropyl]succinate, diphenyl succinate,di[4-methylphenyl]succinate, di-[2-methylphenyl]succinate,di-[4-chlorophenyl]succinate, monoethyl-monophenyl succinate, anddicyclohexyl succinate.

The disuccinates V and the nitriles of the formula VI or VII are knowncompounds and may be prepared by known methods.

This particular process of the invention is carried out in the absenceof any solvent in the temperature range from 70° C. to 200° C., with thepreferred range being from 80° to 140° C.

A process for the synthesis of1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrroles starting from benzonitrileand ethyl bromoacetate in the presence of activated zinc-copper coupleis described in Tetrahedron Lett. 1974, 2549-52. However, the yieldsobtained up to now have been unsatisfactory.

By starting from a succinate and an aromatic nitrile under specificreaction conditions as described in U.S. Pat. No. 4,579,949 the desiredpyrrolo[3,4-c]pyrroles are obtained in substantially higher yield.However, the process requires the use of very special inert organicsolvents. To obtain high yields as claimed in the patent, besides beinginert, the solvents need to be of high purity and particularlysubstantially anhydrous. Furthermore, the solvents need to beregenerated for reuse after their use in the process. Regeneration ofsolvents in high purity and particularly in substantially anhydrous formmakes the process further cumbersome. Moreover, the use of solvent alsoreduces the productivity and requires higher energy consumption therebymaking the process less economical. For example, the U.S. Pat. No.4,579,949 also describes the use of 5 to 20 parts by weight of solventper 1 part by weight of reactants. Other disadvantages of asolvent-based process include environmental (VOC), hygiene and safetyissues.

Accordingly, the present invention provides a process for thepreparation of 1,4-diketopyrrolo[3,4-c]pyrroles of the formula IIIessentially in the absence of any organic solvent and in the presence ofa strong base at elevated temperature, thereby alleviating the saiddisadvantages of the state-of-the-art solvent based process. The presentinvention also provides a process of preparation of the corresponding1,4-diketopyrrolo[3,4-c]pyrrole pigments of the formula IV in theirfinely divided suitable pigmentary form.

It is entirely possible to carry out this process not only batch wise,but also continuously. When using disuccinates containing alkyl radicalsand alcoholates which are derived from lower alcohols such as methanol,ethanol, n-propanol, isopropanol or tert-butanol, it may be necessary toremove the lower alcohol formed during the reaction from the reactionmedium continuously in order to obtain higher yields.

A further preferred embodiment of the process consists in using thenitrile to be reacted with the disuccinate in no more than thestoichiometric proportions. It has been found that the yield of finalproduct can usually be further improved by using an excess ofdisuccinate over the nitrile, in which case the optimum amount must bedetermined according to the respective reactants and may be up to 50percent in excess over the stoichiometric amount required with respectto the nitrile.

Further preferred compounds of the general formula I are thequinacridones of formula X

wherein a preferred meaning of M is an alkali metal, D₁, D₂, D₃ and D₄are fluorine, chlorine or bromine atoms or mixtures thereof, methoxy,methyl groups or mixtures thereof, cyano, dimethylamino,trifluoromethyl, tert-butyl or acetyl groups;the isoindolinone compounds of formula

wherein M is an alkali metal, preferably sodium or potassium, Z₁ halogenor hydrogen, and Y₁ is an aromatic residue of the formula

the quinophthalone of formula

the isoindoline of Formula

wherein E₁ through E₄ represent CN, CONH-alkyl or CONH-aryl. E₁/E₂ andE₃/E₄ can also be members of a mono- and poly-heterocyclic ring systemsor combinations thereof. Examples of such compounds are the derivativesof: C.I. Pigment Yellow 139, C.I. Pigment Yellow 185, C.I. PigmentOrange 66, Pigment Orange 69, Pigment Red 260, Pigment Brown 38.

Further compounds of the formula A(H)_(x)(H)_(y) (II) suitable for theformation of the compounds of formula A(D)_(x)(E)_(y) (I) are forexample

-   a) the azo pigments: C.I. Pigment Yellow 154, C.I. Pigment Yellow    180, C.I. Pigment Yellow 181, C.I. Pigment Yellow 182, C.I. Pigment    Orange 36, C.I. Pigment Orange 62, C.I. Pigment Orange 64, C.I.    Pigment Red 176, C.I. Pigment Red 185, C.I. Pigment Brown 23;-   b) the perylene pigments: C.I. Pigment Red 224, C.I. Pigment Violet    23;-   c) the perinone pigment: C.I. Pigment Orange 43;-   d) the anthraquinone pigments: C.I. Pigment Red 177, C.I. Pigment    Blue 60;-   e) the pyrazoloquinazolone pigments: C.I. Pigment Orange 67, C.I.    Pigment Red 251;-   f) the phthalocyanine pigment: C.I. Pigment Blue 16;-   g) the heterocyclic pigments: thiazine (THI) pigments such as    claimed in WO 9832800 and benzimidazolone-dioxazine pigments such as    claimed in DE 4442291.

The present invention is also related to a process of making a finelydivided particulate compound of formula A(H)_(x)(H)_(y) (II) from thecorresponding initial crude compound of the same formula.

Production of organic pigments, which are particulate organic solids,usually involves two processing stages (Hugh Smith in Pigment HandbookVol I page 414, ed. P. Lewis, John Wiley 1988). The first stage involvesthe synthesis of the corresponding chemical moiety in which the productis usually formed in a large crystalline form not suitable for pigmentapplications. In a subsequent process the primary particles aresub-divided and then tailored to meet the requirements of theirapplication. Such processes of finishing or conditioning of pigmentsare, however, usually very energy consuming (such as wet and drymilling) or highly polluting (such as acid pasting or acid swelling).Finishing of organic pigments such as isoindolinone pigments via theiralkali metal salts in situ is also described. However, the use of largequantities of an organic solvent is imperative. Moreover, the processalso requires the use of very special inert organic solvents. Besidesbeing inert, the solvents need to be substantially anhydrous.Furthermore, the solvents need to be regenerated for reuse in a separateprocess after their use in the process. Regeneration of solvents,particularly the most preferred alcoholic solvents, in substantiallyanhydrous form makes the process further cumbersome. Moreover, the useof large quantities of solvent also reduces the productivity andrequires higher energy consumption thereby making the process lesseconomical.

The present process has the advantage that the use of solvent is notimperative in the finishing stage. Moreover, if the most preferredalcoholic solvents are used in place of and/or in combination withwater, they need not, be anhydrous, thereby making their regenerationvery facile and economical. The final pigment composition is obtainedwith a fine particle size and the desired application properties such asexcellent dispersability, high color strength, high weatherability, andhigh saturation of color.

In a preferred method, water or a mixture of water and a primary or asecondary is used as medium of hydrolysis.

One can also use additives known in the state-of-the-art to control theparticle size of the pigment composition. It's possible as well tocontrol the particle size of the pigment composition by heating underpressure the final pigment suspension at the end of the precipitation.

Depending on the pigments and on the conditions of hydrolysis, pigmentswith a particle size below 2 microns are obtained.

When the formation of the desired particulate crystal size and shape iscomplete, the conditioned pigment is isolated by filtration, the presscake being washed with water and/or an organic solvent, preferablymethanol, followed by water and dried. Good results can be obtained byperforming the filtration in acidic conditions.

One can also use additives known in the state-of-the-art to control theparticle size of the pigment composition. It's possible as well tocontrol the particle size of the pigment composition by heating underpressure the final pigment suspension at the end of the hydrolysis.

A further objective of the present invention is to provide pigmentdispersions, which possess high stability and good transparency, and aprocess for preparing them.

Recent pigment applications such as color filters and ink jetapplications are placing stringent requirements on the coloristic andprocessing properties of pigments. The pigments are required to possessclean, strong and bright shades to allow the opening-up of a large colorarea. Furthermore, they should be able to be used not only as anindividual pigment but also as an element for combination in, say,trichromatic pigmentations. In terms of technical application it provesadvantageous to apply the pigment as dispersion, since it is thenpossible to avoid laborious mixing and milling operations, whichrepresent an additional hygiene burden. Moreover, the dispersions makethe pigmentation process more reproducible, since there is a morehomogeneous distribution of the pigment particles than in the powderform.

On economic grounds even for classical applications such as printinginks, it is particularly desirable to employ concentrated, stabledispersions, which require little space on transportation or storage andat the same time possess good stability.

Moreover, for ecological reasons and stringent VOC regulatoryconsiderations in many countries aqueous dispersions rather thansolvent-based dispersions are highly desired.

Alkali metal salts of pigments of the present invention used as latentpigments are particularly suitable for preparation of all such pigmentdispersions, typically known for example from U.S. Pat. No. 6,302,953;U.S. Pat. No. 6,462,125, 4; U.S. Pat. No. 4,986,851; WO 99/01511; WO03/008510. Surprisingly, since alkali metal salt pigments getauto-dispersed upon incorporation and by in situ hydrolysis, no specialdispersing equipment such as bead-mills or kneaders are required fortheir dispersion, unlike any state-of-the-art processes for thepreparation of pigment dispersions.

Accordingly, from U.S. Pat. Nos. 4,597,794 and 5,085,698 it is known toprepare fine pigment dispersions having an average particle sizedistribution of 0.015-0.5 micrometers, which are obtained with theaddition of stabilising copolymers by mechanical comminution andsubsequent selection techniques, such as filtration or centrifuging, inorder to remove coarse particles. A disadvantage of these processes isthe extremely time-consuming and energy-intensive milling process, whichmay last for several days and requires high frictional energy. Themilled product has a broad particle size distribution and rough surfacesowing to the mechanical stress. Excessively large pigment particles, orthose with a roughened surface, lead to a loss of transparency. Smallerparticles, on the other hand, tend to form aggregates, which in thecourse of the dispersion process are broken up by known techniques, bymeans of high-energy input in the form, for example, of ultrasound. Oneconsequence of the propensity of smaller particles to aggregate is theirflocculation tendency, and so these dispersions are inherently unstable.

The disadvantages described can be alleviated only in part by othertechniques, such as evaporation methods (see U.S. Pat. Nos. 5,030,669and 5,106,533) or the preparation of fine dispersions under highpressure (WO 96/14925). Moreover, these techniques require specialapparatus for their application.

U.S. Pat. No. 6,211,347 provides a process for preparing pigmentdispersions comprising subjecting a mixture comprising a latent pigmentknown from EP-A 654 711, a polymer and a solvent to thermal, chemical orphotolytic treatment. The disadvantages of such latent pigments andparticularly the drawbacks of their use as described above are therebynot adequately addressed.

The present invention, accordingly, provides a process for preparingpigment dispersions composed of a pigment, a polymer and/or adispersant, a liquid medium and optionally an alkali metal salt of anorganic acid which comprises

1) incorporating a compound of formula A(D)_(x)(E)_(y) (I) into amixture A of a polymer, a liquid medium, a polymer and/or a dispersant,and then optionally adding an organic acid, or

2) optional incorporation of an organic acid to a mixture B comprisingof a compound of formula A(D)_(x)(E)_(y) (I), a polymer and/or adispersant, and a liquid medium, or

3) simultaneous incorporation of a compound of formula A(D)_(x)(E)_(y)(I) and an organic acid, into a mixture C comprising a polymer and/or adispersant and a liquid medium, or

any other permutations and combinations of the above procedures.

Organic acids suitable for this process are aliphatic, or aromaticpoly-carboxylic or poly-sulphonic acids or poly-phosphonic acidscontaining up to 4 acid groups acids for the each aliphatic or thearomatic rest. Preferred organic acids acid are the ones that, besidesinteracting with the alkali metal salt of the pigment, can act both as adispersing as well as an anti-microbial agent. Typical acids are up toC18 aliphatic acids, aromatic acid such as benzoic acids, phthalic acidsterephthalic acids, isophthalic acids trimesic acids and pyromeliticacids; benzene, alkylbenzene, naphthalene and alkylnaphthalene sulphonicor phosphonic acids.

Typical state-of-the art liquids are water organic solvents arealiphatic C₁-C₄ alcohols, such as methanol, ethanol, n-propanol,isopropanol, n-butanol, tert-butanol, ketones such as acetone methylethyl ketone, methyl isobutyl ketone or diacetone alcohol, and alsopolyols, cellosolves and carbitols, such as ethylene glycol, diethyleneglycol, triethylene glycol, glycerol, propylene glycol, ethylene glycolmonomethyl or monoethyl ether, propylene glycol methyl ether,dipropylene glycol methyl ether, tripropylene glycol methyl ether,ethylene glycol phenyl ether, propylene glycol phenyl ether, diethyleneglycol monomethyl or monoethyl ether, diethylene glycol monobutyl ether,triethylene glycol monomethyl or monoethyl ether, and alsoN-methyl-2-pyrrolidone, 2-pyrrolidone, N,N′-dimethylformamide orN,N′-dimethylacetamide.

However, the process is particularly suitable for the preparation ofaqueous pigment dispersions.

The fine pigment dispersions prepared by the process of the inventionpreferably possess an average particle size distribution of 0.02-0.6micrometers, with particular preference 0.03-0.5 micrometers and, withvery particular preference, 0.06-0.4 micrometers. The particle sizedistribution was determined by the Joyce-Loebl disk centrifuging method.

The dispersants can be ionic or non-ionic in character, preferably whichpossess a preferred spatial orientation in solvents of differentdensity. The aqueous dispersions, for example, comprise large moleculesconsisting of a hydrophilic head and a hydrophobic tail for exampleFluorad FC-170, a non-ionic fluorine-containing surfactant from 3M Inc.(or such as OLOA™ 1200 from Chevron Corp., Richfield, Calif., Amoco™9250, from Amoco Chemical Co., Naperville, Ill.). The resultingdispersions preferably contain 20% by weight, with particular preference10% by weight and, with very particular preference, 5% by weight ofadditives and may if desired include further co-solvents, examples beingcyclohexanone, cyclopentanone, N,N′-dimethylformamide and dimethylsulfoxide.

Polymers for aqueous pigment dispersions are preferably polymersconsisting of a hydrophilic and hydrophobic part. The former can beionisable, and form salts, or non-ionisable.

The polymers are preferably random, block or graft polymers.

The hydrophilic part of the polymers is formed, for example, frommonomers which in addition to functional groups such as alcohol,carboxyl, carboxamido, carboxylato or sulfo groups comprise sulfato,cyanato or carboxylic anhydride groups, or ether groups such as ethyleneor propylene oxide groups, and in addition a polymerizable vinyl orvinylene radical, such as an acrylic or methylacrylic, crotyl,sulfoethylmethylacrylic, sulfopropylmetlhylacrylic, vinylnaphthyl,vinylphenyl or vinyltolyl radical, itaconyl radical, for exampleitaconyl monoesters, maleic acid or maleinyl radical, for example maleicmonoesters, fumaryl radical, for example fumaryl monoesters, andespecially vinylbenzoic acid. The monoesters are for example monoestersof itaconic, maleic or fumaric acid.

Preference is given to monomers which possess carboxyl, carboxylicanhydride, sulfonate or sulfate groups as functional groups. Particularpreference is given to carboxyl or carboxylic anhydride groups, forexample vinylbenzoic acid or maleic anhydride.

Monomers which form the hydrophobic part of the polymers are preferablyfor example selected from the group of the apolar monomers consisting ofstyrene, styrene derivatives, such as C₁-C₄ alkyl-substituted styrene,and vinyl chloride, vinylnaphthalene, vinylnaphthalene derivatives, suchas C₁-C₄ alkyl-substituted vinylnaphthalene, vinyltoluene, alpha.-, m-,p- or m/p-vinyltoluene and aliphatic C₁₂-C₁₈ alkenes.

Preferred hydrophobic apolar monomers are for example styrene,vinyltoluene and octadecene.

The copolymers chosen preferably have a narrow molar mass distributionof 1-2 Mw/Mn (where Mw is the mass average and Mn the number average).

For water-free pigment dispersions use is made for example of acrylate,methacrylate, styrene and vinyl polymers.

In a particularly preferred embodiment use is made of polyvinyl butyratefor ethanolic dispersions and of methyl methacrylate for dispersionswith methyl ethyl ketone as solvent, or to copolymers of methylmethacrylate and butyl acrylate for pigment dispersions with chloroformas solvent.

Preferred polymers for aqueous pigment dispersion are composed forexample of carboxyl-containing polymers, for example styrene,vinyltoluene and vinylbenzoic acid, or vinylbenzoic acid and apolarmonomers, and of styrene and maleic anhydride or of copolymers oflong-chain alkenes (C₁₂-C₁₈) with maleic anhydride, for examplestyrene-maleic anhydride, styrene-vinyltoluene-vinylbenzoic acid oroctadecene-maleic anhydride.

A preferred embodiment of the process of the invention relates to thepreparation of aqueous basic pigment dispersions from a latent pigmentwith a solution of a copolymer comprising vinylbenzoic acid and anon-polar monomer or with a solution comprising a carboxyl-containingpolymer.

There now follows a series of examples that serve to illustrate theinvention.

EXAMPLE 1

2475 g of p-chlorobenzonitrile, 2181.6 g diisopropyl succinate and2869.2 g sodium tert-butylate are placed at 20-25° C. in a 10000 ml “AllIn One Reactor”® of (Drais Mannheim Germany). Under stirring andnitrogen flow the mixture is heated to 100° C. within 60 minutes. From80° C. onwards the reaction mixture becomes considerably thicker and isfinally converted into a paste. From 80-85° C. onwards a rapid formationof alcohol vapours is observed. The temperature is maintained at 99° to100° C. for three hours, thereby allowing the mixture of isopropylalcohol and tert-butyl alcohol to distil off. The reaction mass becomescrumbly and finally largely disintegrates into an almost semi-powderymaterial. The reaction mixture is heated to 120° C. in 30 minutes andkept at 120° C. for 30 minutes. The mixture is cooled to 50° C. Thematerial is emptied into a polyethylene sack, tightly fitted to theoutlet of the reactor; affording 3248 g (90% of theory, based onp-chlorobenzonitrile) of pigment of the formula XIX. Approximately 200 g(5.54% of theory, based on p-chlorobenzonitrile) of the product arestill contained in the reactor to be used in the next batch. The totalyield thus corresponds to approximately 3448 g (approximately 95.54% oftheory, based on p-chlorobenzonitrile).

This product produces an intense red colour when dispersed with stirringinto a state-of-the-art waterborne paint system.

EXAMPLE 2

For the hydrolysis, 1000 g product of the example 1 are slowly added toa mixture of 7000 ml of methanol and 35 g of acetic acid at roomtemperature. The mixture is then heated to reflux and kept at refluxtemperature for two hours. The resultant pigment suspension is filteredat about 50° C., washed with methanol and water until the washings runcolourless, and dried at 80° C. in vacuum, affording 845 g (95% oftheory, based on compound of formula XIX) of pure pigment of the formulaXX

which colours PVC-red.

EXAMPLE 3

1545 g of benzonitrile, 2242.5 g di-tert-butyl succinate and 3024 gpotassium tert-butylate are placed at 20-25° C. in a 10000 ml “All InOne Reactor” of (Drais Mannheim Germany). Under stirring and nitrogenflow the mixture is heated to 100° C. within 60 minutes. From 700onwards the reaction mixture becomes considerably thicker and is finallyconverted into a paste. From 70-75° onwards a rapid formation of alcoholvapours is observed. The temperature is maintained at 99 degree to 100°C. for three hours thereby allowing, the tert-butyl alcohol to distiloff. The reaction mass becomes crumbly and finally largely disintegratesinto an almost semi-powdery material. The reaction mixture is heated to120° C. in 30 minutes and kept at 120° C. for 30 minutes. The mixture iscooled to 50° C. The material is emptied into a polyethylene sack,tightly fitted to the outlet of the reactor and then worked up as inexample 2 yielding 1840 g (85% of theory, based on benzonitrile) of purepigment of the formula XXI

EXAMPLE 4

2750 g of p-chlorobenzonitrile and 2950 g sodium iso-propylate areplaced at 20-25° C. in a 10000 ml “All In One Reactor” of (DraisMannheim Germany). Under stirring and nitrogen flow the mixture isheated to 90° C. within 60 minutes. As soon as this temperature has beenreached, 2424 g diisopropyl succinate are added over 145 minutes bymeans of a metering pump. The temperature is kept constantly at 98-99°C. and isopropyl alcohol is distilled off. The temperature is maintainedat 99 to, 100° C. for two hours. The reaction mixture is heated to 120°C. in 30 minutes and kept at 120° C. for 30 minutes. The mixture iscooled to 50° C. The material is emptied into a polyethylene sack,tightly fitted to the outlet of the reactor; the yield is 3490 g(approximately 87% of theory, based on p-chlorobenzonitrile) of thecompound of formula XIX.

For the hydrolysis, 1000 g of the above reaction mixture is slowly addedto 10000 ml of water at 80° C. temperature. The resultant pigmentsuspension is heated to 95° C. and kept at 95° C. for two hours.Thereafter, it is filtered at about 80° C., washed with water until thewashings run colourless, and dried at 80° C. in vacuum; affording 872 g(98% of theory, based on the compound of formula XIX) of a very finelydivided pigment of the formula XX.

The crude pigment is then finished by treating with seven volume partsof dimethyl formamide at 130° C. for three hours. The suspension isfiltered at 100° C., washed with the same volume of dimethyl formamideheated to 110° C. followed by water at 70° C. The press cake is dried at100° C. yielding a bright red product.

EXAMPLES 5-15

2-kilo mole of a nitrile of the formula R—CN, wherein R has the meaningindicated in Table 1, and 3960 g of sodium tert-amylate are placed at20-25° C. in a 10000 ml paddle drier (TurbuDry®, Drais Mannheim Germany)The mixture is heated under nitrogen to the temperature indicated inTable 1. As soon as this temperature has been reached, 2626 ml ofdi-isopropyl succinate are added by means of a metering pump over theperiod of time also indicated in Table 1 and with continuous stirring.The indicated temperature is maintained and the alcohol mixture formedis allowed to distil off. When the addition is complete, the reactionmixture is kept at the same temperature for 2 hours and hydrolysed andworked up as in Example 2 to give the pigments of the formula XXII

wherein R has the meaning given in Table 1, in the indicated yield.

TABLE 1 Reaction Addition Yield Shade in Temperature Time in based onPVC Example R ° C. Minutes Nitrile (0.1%) 5

 98-100 120 81.5 Red 6

90-92 130 75.9 Red 7

95-97 180 73.2 Orange 8

105-110 240 62.1 Reddish- Violet 9

90-95 100 51.1 Yellowish Red 10

105-110 120 58.3 Red 11

107-112 110 61.7 Red 12

95-97 90 25.6 Orange 13

90-92 60 45.5 Red 14

90-95 90 32 Red 15

 99-100 63 37 Red

EXAMPLES 16-20

1.0 mole of a nitrile of the formula R′—CN and 1.0 kilo mole of theformula R″—CN, wherein R′ and R″ are different and are as defined inTable II (Examples 16-20) and 3.4 kilo mole of sodium tert-amylate areplaced at 20-25° C. in a 10000 ml “All In One Reactor”® (of DraisMannheim Germany). By means of a metering pump, 1.2 kilo moles ofdiisopropyl succinate are added at the reaction temperature indicated inTable II over the period of time also indicated therein, whilecontinuously distilling off the alcohol mixture. When the addition iscomplete, the mixture is kept for 2 hours at the reaction temperatureand then hydrolysed and worked up as in Example 2 to give the pigmentmixture of the formulas XXIII, XXIV and XXV of Table 2.

TABLE 2 XXIII

XXIV

XXV Reaction Yield in Shade in Temperature % of PVC Example R′ R″ ° C.Nitrile (0.2%) 16

 95-100 69.7 Red 17

 95-100 57.7 Scarlet 18

105-110 39.6 Bluish Red 19

 95-100 82.7 Red 20

110-115 67 Orange

EXAMPLE 21

1786 g of the crude diketopyrrolopyrrole pigment C.I. Pigment Red 254,3000 g of tert-butyl alcohol and 960 g of sodium tert-butylate areplaced in a 10000 ml “All In One Reactor”® of (Drais Mannheim Germany)at 30° C. Under stirring and nitrogen flow the mixture is heated to 80°C. and maintained at 80 for 1 hour. From 50° C. onwards the reactionmixture becomes considerably thicker and is finally converted into apaste. Thereafter, the mixture is slowly heated from outside to approx.90° C. After reaching an inside temperature of 85 C a vacuum of 800 mbaris applied at the outlet of the condenser which is then graduallyreduced to 50 mbar, thereby allowing the tert-butyl alcohol to distiloff. The reaction mass becomes crumbly and finally largely disintegratesinto an almost semi-powdery material. The mixture is stirred for another30 minutes at 90° C. under vacuum of 50 mbar. The reaction mixture iscooled to 80° C. The material is emptied into a steel drum affording1950 g of the product of the formula XIX. Approximately 60 g of theproduct are still contained in the reactor to be used in the next batch.The distillate is also used for the next batch.

EXAMPLES 22-26

Using the corresponding commercially available crude pigments in placeof Pigment Red 254 in example 21 and/or the corresponding molar quantityof potassium tert-butylate in place of sodium tert-butylate, thefollowing compounds of general formula XXVI of Table 3 are obtained

TABLE 3 XXVI

Example Starting Material Ra M Color of Solid 22 Pigment Red 255

Na Red 23 Pigment Red 264

Na Bluish Red 24 Pigment Orange 73

Na Orange 25 Pigment Red 272

K Red 26 Pigment Red 71

Na Orange

EXAMPLE 27

1527.4 g diisopropyl succinate, 1732.5 g of p-chlorobenzonitrile and2013 g sodium tert-butylate are placed in a 10000 ml “All In OneReactor”® of (Drais Mannheim Germany) at 20-25° C. Under stirring andnitrogen flow the mixture is heated to 87° C. (inside temperature). From50° C. onwards the reaction mixture becomes considerably thicker and isfinally converted into a paste. As soon as the inside temperature of 87°C. is reached, a vacuum of 800 mbar is applied at the outlet of thecondenser which is then gradually reduced to 50 mbar, thereby allowingthe mixture of isopropyl alcohol and tart-butyl alcohol to distil off.The inside temperature first drops to 75° C. and thereafter rises againto 85° C. as soon as the mixture of alcohols is completely distilledoff. The reaction mass becomes crumbly and finally largely disintegratesinto an almost semi-powdery material. After the distillation of theresidual mixture of alcohols, the reaction mixture is stirred foranother 30 minutes at 87° C. under vacuum of 50 mbar. The mixture iscooled to 60° C. and the material is emptied into a steel container. Theyield is 2950 g of the crude compound of formula XIX of example 21 of81.4% purity (approximately 95% of theory, based onp-chlorobenzonitrile).

EXAMPLES 28-33

Using the corresponding nitriles of formula VI in place ofp-chlorobenzonitrile in example 27 the following compounds of Table 4are obtained

TABLE 4 XXVII

Example R_(b) M Color of Solid 28

Na Red 29

Na Red 30

Na Red 31

Na Red 32

Na Red 33

K Red

EXAMPLE 34

For the hydrolysis, 1000 g product of the crude compound of formula XIXof example 27 is slowly added to a mixture of 7000 ml of methanol and330 g of acetic acid at room temperature. The mixtures is then heated toreflux and kept at reflux temperature for two hours. The resultantpigment suspension is filtered at about 50° C., washed with methanol andwater until the washings run colourless, and dried at 80° C. in vacuum,affording 720 g of the pure pigment of formula XX.

EXAMPLES 35-40

Using the corresponding starting materials of Table 4 (examples 28-33)in example 27 the compounds of Formula XXVIII in Table 5 are obtained

TABLE 5 XXVIII

Ex- am- Color ple Starting Material R_(b) M of Solid 35 Example 28

Na Orange-Red 36 Example 29

Na Red 37 Example 30

Na Red 38 Example 31

Na Orange-Red 39 Example 32

Na Orange-Red 40 Example 33

K Red

EXAMPLE 41

Compound of formula XX, obtained by using compound of formula XIX ofExample 21 as starting material in example 34

EXAMPLES 42-46

Compounds of formula XXIX (Table 6), obtained by using the correspondingcompounds of formula XXVI of Table 3 as starting materials in example 34

TABLE 6 XXIX

Ex- am- Color ple Starting Material Ra of Solid 42 Example 22

Red 43 Example 23

Bluish Red 44 Example 24

Orange 45 Example 25

Red 46 Example 26

Orange

EXAMPLE 47

A 500 ml glass reactor is charged with 150 ml of anhydrous ter-amylalcohol under nitrogen. 4.6 g (0.2 moles) of sodium are added theretoand the mixture is heated to and maintained at 100-105° C. for 12 hours.To the resulting solution are then added at 80° C., 20.6 g (0.15 moles)of 4-chlorobenzonitrile. Subsequently 20.1 g (0.01 moles) of diisopropylsuccinate are metered in at 96° C. over 3 hours. The isopropanol formedduring the reaction along with some tert-amyl alcohol is allowed todistil off simultaneously during the addition. The reaction mixture isstirred for another 4 hours after the addition of diisopropyl succinateis complete. Thereafter the reaction mixture is transferred to a 500 mlround bottomed flask and the residual tert-amyl alcohol is distilled offon a rotavap (Buechi) under vacuum to yield the compound of Formula XIXas a dark red powder.

EXAMPLE 48

Hydrolysis of the compound XIX of example 47 to a compound of Formula XXas described in example 34

EXAMPLE 49

1700 g of the crude dimethyl quinacridone pigment C.I. Pigment Red 122,3500 g of tert-butyl alcohol and 960 g of sodium tert-butylate areplaced in a 10000 ml “All In One Reactor”® of (Drais Mannheim Germany)at 30 C. Under stirring and nitrogen flow the mixture is heated to 80°C. and maintained at 80° C. for 3 hours. From 50° C. onwards thereaction mixture becomes considerably thicker and is finally convertedinto a paste. Thereafter, the mixture is slowly heated to approx. 90° C.After reaching an inside temperature of 85° C. a vacuum of 800 mbar isapplied at the outlet of the condenser which is then gradually furtherreduced to 50 mbar, thereby allowing the tert-butyl alcohol to distiloff. The inside temperature first drops to 75° C. and thereafter risesagain to 85° C. as soon as the alcohol is completely distilled off. Thereaction mass becomes crumbly and finally largely disintegrates into analmost semi-powdery material. The mixture is stirred for another 30minutes at 85° C. under vacuum of 50 mbar. The reaction mixture iscooled to 60° C. The material is emptied into a steel drum affording1890 g of the product of the formula XXX.

Approximately 30 g of the product are still contained in the reactor tobe used in the next batch. The distillate is also used for the nextbatch.

EXAMPLES 50-53

Starting from the corresponding Pigments, compounds of Table 7 areobtained following the procedure described in Example 49

TABLE 7 Example Starting Material Product Formula 50 Pigment Yellow 138

XXXI 51 Pigment Yellow 110

XXXII 52 Pigment Yellow 109

XXXIII 53 Pigment Yellow 139

XXXIV

EXAMPLE 54

To a mixture of 400 ml of water, 1.6 g of phthalic acid, 0.7 g of a 2%(percent by weight) solution of a surface-active substance (FluoradFC-171 from 3M Inc.) dissolved in diethylene glycol are added 4 g of thecompound of formula XIX of Example 21 under stirring followed by theaddition of 10 g of octadecene-maleic anhydride copolymer (MW 50 000,from Scientific Polymer Products Inc.) dissolved in 100 ml of dioxane.After mixing, dioxane is distilled off on a rotary evaporator underreduced pressure and the red dispersion is concentrated to approximately410 g. The resulting dispersion is homogeneous and transparent. It has aviscosity of 2.16 mPas at 25.degree. C. After several days, no tendencyto precipitate is observed. A sample is diluted 50-fold with water andthe transmission spectrum is measured in a 1 mm cell. At the maximum(520 nm) the absorption is 1.42, while at 660 nm it is only 0.1, whichpoints to fine particles with good transparency. In addition, electronmicrographs show that all particle dimensions are below 0.5 micrometers.

EXAMPLE 55

3 g of the pigment dispersion of Example 54 are mixed with 0.75 g of a2% (percent by weight) solution of a surface-active substance (FluoradFC-171 from 3M Inc.) dissolved in diethylene glycol. The resulting inkis tested in a “Quietjet” (Hewlett-Packard) thermal inkjet printer,which is fitted with a plastic device provided to accommodate the ink. Aclear, sharp print quality is obtained, as is a surface coverage at apeak optical density of 0.5 (this value is measured with a spectrometerin reflection mode, which is subtracted from the reflection of thepaper).

The ink shows no tendency to bleed or penetrate through customarycommercial copier paper.

EXAMPLE 56

10 g of the pigment dispersion of Example 54 are mixed with 0.8 g of a2% (percent by weight) solution of a surface-active substance (FluoradFC-171 from 3M Inc.) and diethylene glycol and with 1.2 g of diethyleneglycol, 0.5 g of 2-propanpol, 0.2 g of morpholine and 0.2 g of butylsulfoxide. The resulting ink is tested in a “QuietJet” (Hewlett-Packard)thermal inkjet printer, which is fitted with a plastic device providedto accommodate the ink. A clear, sharp print quality is obtained, as isa surface coverage with a maximum optical density of 1.09 (this value ismeasured with a spectrometer in reflection mode, which is subtractedfrom the reflection of the paper).

The ink shows no tendency to bleed or penetrate through customarycommercial copier paper.

EXAMPLE 57

To a mixture of 25 parts of a styrene/acrylic acid copolymer acrylateresin (for example as described in WO 03/08510), 5 parts of a dispersant(C₁₃₋₁₅-alkyl)-O—(CH₂CH₂O)_(9.5)—CH₂COONa, 15 parts of propylene glycoland 35 parts of water are added 20 parts of a compound of formula XIX ofexample 21 under stirring. To the resulting mixture is then added 8parts of phthalic acid. The resulting pigment dispersion does not needto be milled using for example a sand mill.

The pigment dispersion shows excellent flow properties and storagestability. It is particularly suitable for ink-jet applications.

EXAMPLE 58

20 parts of the compound XIX of example 21 was added to a mixture of 30parts of propylene glycol monomethyl ether acetate and 50 parts of anacrylic resin (obtained by polymerizing methacrylic acid, butylacrylate, styrene, hydroxyethyl acrylate at a molar ratio of25/50/15/10; molecular weight: 12,000; solid content: 30%) and 8.3 partsof terephthalic acid. Thereby a red base color for color filters wasobtained (for example of U.S. Pat. No. 6,302,953 without a dispersant).

EXAMPLE 59

40 parts of the compound of formula XIX of example 21 are added to amixture of 7.5 parts of a polyphenyloxalate, 7.5 parts ofα-methyl-omega-hydroxy-polyethylenglykolether (MW 470-530 g/mol) and 45parts of water under stirring followed by the addition of 15.75 parts oftrimesic acid. The resulting pigment dispersion does not need to bemilled using for example a sand mill.

The pigment dispersion shows excellent flow properties and storagestability. It is particularly suitable for tinting of architecturalpaints.

1. A process for the preparation of a compound of formula III

wherein both M represent an alkali metal and each of R₁ and R₂independently of the other is a carbocylic aromatic radical or aheterocyclic aromatic radical, which process comprises the steps of:providing to a reactor as reactants an unsymmetrical or symmetricaldialkyl or diaryl succinate, or monoalkyl monoaryl succinate ordicycloalkyl succinate of formula V

wherein each R₃ and R₄ independently of the other is an alkyl or acycloalkyl or an aryl radical, with two moles of nitrile of formula VIR₁—CN  (VI)or of formula VIIR₂—CN  (VII) for at least each mole of succinate or with 0.0 to 2.0 moleof a nitrile of the formula (VI) and 2.0 to 0.0 mole of the nitrile ofthe formula (VII), and further, providing 2 to 5 moles of a strong baseat a temperature of 20° C.-25° C., then subsequently reacting the saidreactants in the presence of the strong base and essentially in theabsence of any organic solvent to condense the reactants at atemperature of 70° C. to 200° C.
 2. A process according to claim 1,wherein essentially no organic solvent is present.
 3. A processaccording to claim 1, wherein said strong base is an alkali metal, analkali metal amide, an alkali metal hydride, an alkali metal alcoholateor an alkaline earth metal alcoholate.
 4. A process according to claim1, wherein the nitrile is a single nitrile of the formula VI or VII. 5.A process according to claim 1, wherein the disuccinate V is asymmetrical dialkyl succinate containing 1 to 18 carbon atoms in eachalkyl moiety.
 6. A process according to claim 1, wherein the disuccinateV is a symmetrical dialkyl succinate, wherein alkyl is sec- ortert-alkyl.
 7. A process according to claim 1 wherein each of R₁ and R₂independently of the other is phenyl or phenyl substituted by one or twochlorine atoms, by one or two methyl groups, by methoxy, bytrifluoromethyl, by cyano, by methoxycarbonyl, by tert-butyl, bydimethylamino or by cyanophenyl; naphthyl; biphenylyl; pyridyl or saidpyridyl substituted by amyloxy; furyl or thienyl.
 8. A process accordingto claim 7 wherein each of R₁ and R₂ independently of the other isphenyl, 3-chlorophenyl, 4-chlorophenyl, 3,5-dichlorophenyl,4-methylphenyl, 4-methoxyphenyl, 3-trifluoromethylphenyl,4-trifluoromethylphenyl, 3-cyanophenyl, 4-cyanophenyl,4-methoxycarbonylphenyl, 4-tert-butylphenyl, 4-dimethylaminophenyl,4-(p-cyanophenyl) phenyl, 1-naphthyl, 2-naphthyl, 4-biphenylyl,2-pyridyl, 3-pyridyl, 4-pyridyl, 6-amyloxy-3-pyridyl, 2-furyl or2-thienyl.
 9. A process according to claim 1, wherein the strong base isan alkali metal alcoholate.
 10. A process according to claim 9, whereinthe alkali metal alcoholate is derived from a secondary or tertiaryalcohol.